In recent years, composite materials including organic–inorganic systems have drawn special attention due to their enhanced properties such as adsorbents and heterogeneous catalysts. At the same time, large-scale production of environmentally benign functionalized biopolymers, such as chitosan (CS), allows for constantly developing new materials, since CS reveals remarkable properties as a stabilizing agent for metal-containing compounds and enzymes and as an adsorbent of organic molecules. This review is focused on CS-based materials and on the composite systems including CS-oxide and CS-metal composites in particular for application as adsorbents and supports for catalytically active metal nanoparticles and enzymes.

Here, we developed magnetically recoverable biocatalysts based on magnetite nanoparticles coated with an ultra-thin layer (about 0.9 nm) of chitosan (CS) ionically cross-linked by sodium tripolyphosphate (TPP). Excessive CS amounts were removed by multiple washings combined with magnetic separation. Glucose oxidase (GOx) was attached to the magnetic support via the interaction with N-hydroxysuccinimide (NHS) in the presence of carbodiimide (EDC) leading to a covalent amide bond. These steps result in the formation of the biocatalyst for D-glucose oxidation to D-gluconic acid to be used in the preparation of pharmaceuticals due to the benign character of the biocatalyst components. To choose the catalyst with the best catalytic performance, the amounts of CS, TPP, NHS, EDC, and GOx were varied. The optimal biocatalyst allowed for 100% relative catalytic activity. The immobilization of GOx and the magnetic character of the support prevents GOx and biocatalyst loss and allows for repeated use.

Here, we report the development of a novel bifunctional nanobiocatalyst for a one-pot cascade transformation of carboxymethyl cellulose (CMC) to D-sorbitol. The nanobiocatalyst is based on magnetic nanoparticle aggregates (MNAs) functionalized with chitosan (CS) cross-linked by tripolyphosphate (TPP). It contains two types of catalytic sites: cellulase (Cel, 5 wt.%) and Ru (3 wt.%) nanoparticles (NPs) of 0.7 nm in diameter. To optimize the nanobiocatalyst structure and composition, we first synthesized the biocatalyst, MNA-CSP-Cel (CSP stands for the CS layer cross-linked by TPP), as well as the nanocatalyst, MNA-CSP-Ru, and studied them in the one-step reactions of hydrolysis and hydrogenation, respectively. The data obtained allowed us to optimize the composition and properties of the bifunctional nanobiocatalyst, MNA-CSP-Ru-Cel, and to choose the best reaction conditions for the cascade process. MNA-CSP-Ru-Cel was characterized using transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and porosity measurements. The knowledge obtained enabled us to perform a cascade transformation of CMC to D-sorbitol with a yield of 83.2% for 10 h at 70 °C and a hydrogen pressure of 4 MPa. The yield demonstrated in this work is much higher than that reported to date for the same cascade process.

В статье проведено определение антиоксидантной активности образцов различной природы 2 методами. Выявлено, что среди исследованных образцов индивидуальных антиоксидантов наибольшей активностью обладают биологически активная добавка «Pomegranate» и аскорбиновая кислота, наименьшей - глутатион. Среди антиоксидантного сырья наибольшей активностью обладает прополис, имеющий гораздо большую антиоксидантную активность, чем все другие образцы, далее следуют перегородки и кожура граната. Наименьшей активностью из исследованных видов сырья обладает боярышник. In the article, antioxidant activity of samples of different nature was determined by 2 methods. It was revealed that among the examined samples of individual antioxidants, the biologically active additive «Pomegranate» and ascorbic acid have the greatest activity, the smallest is glutathione. Among antioxidant raw materials, propolis has the greatest activity, having a much greater antioxidant activity than all other samples, followed by pomegranate partitions and peels. Hawthorn has the least activity from the raw materials studied.